Health Effects of Suspended Particulate Matter

Judith C. Chow (Judy.Chow@dri.edu)John G. Watson

Desert Research InstituteReno, Nevada, USA

Presented at:

The Workshop on Air Quality Management, Measurement, Modeling, and Health Effects

University of Zagreb, Zagreb, Croatia

24 May 2007

Objectives• Report progress for PM and health

effects

• Explain ultrafine particles and their toxicological/ epidemiological associations

• Identify knowledge gaps and future challenges in PM research

Air Pollution/Health Issue

http://www.epri.com/

Air Quality Decision Making Framework

Emissions (rates, particle

size, and composition)

Transport and

Transformation

Concentrations in Air (composition,

particle size, health indicator)

Human Exposure (outdoor

and indoor)

Human Inhalation

Dose to Target Tissues

Adverse Health Effects

National Research Council, 1998, Research Priorities for Airborne Particulate Matter: I - Immediate Priorities and a Long-Range Research Portfolio

National Research Council (NRC) Reports (1998, 1999, 2001, 2004)

History of Public Policy and PM Science

SCIENCE

1930s-1950s Early Episode studies

1960s-1980s Ecological mortality and inhalation tox. studies

1989-mid 1990s New results from several

epidemiologic studies

U.S. PUBLIC POLICY

1955, 1963 Early national legislation

1967, 1970, 1971 Clean Air Act, amendments,

NAAQS

1987 PM standards revised, TSP-PM10

Pope and Dockery, 2006, JAWMA, 56(6)

History of Public Policy and PM Science (continued)

SCIENCE

1997Vedal’s “Lines that Divide” Growth in PM and health effects research (Vedal,

1997, JAWMA)

2006 “Lines that Connect” Gaps and skepticism (Pope

and Dockery, 2006, JAWMA)

U.S. PUBLIC POLICY

1997-2002 Promulgation of PM2.5 standards,

Legal challenges argued and largely resolved

2006 New proposed standards for

PM2.5 and PM10-2.5

Pope and Dockery, 2006, JAWMA, 56(6)

Particle Size Distribution

0

2

4

6

8

10

0.001 0.01 0.1 1 10 100Particle Aerodynamic Diameter (µm)

Rel

ativ

e M

ass

Co

nce

ntr

atio

n

Accumulation Coarse

PM 10

PM 2.5

Geological Material, Pollen,

Sea Salt

Sulfate, Nitrate, Ammonium,

Organic Carbon, Elemental Carbon, Heavy Metals, Fine

Geological

Condensed Organic

Carbon or Sulfuric Acid Vapors, Clean Environment

Aitken

Condensation Mode

Droplet Mode

Nucleation

Fresh High Temperature Emissions,

Organic Carbon,

Sulfuric Acid, Metal Vapors

Ultrafine (PM 0.1)

Nanoparticles (PM 0.01)

Watson, 2002, JAWMA, 52(6)

Inhalation Properties

0

20

40

60

80

100

120

0.01 0.1 1 10 100

Particle Aerodynamic Diameter (microns)

De

po

sit

ion

(P

erc

en

t)

Rest Normal Exercise

Nose

Lung

Trachea

Mouth (ISO)

Chow, 1995, JAWMA 45(5); Phalen et al., 1991, Radiat. Protect. Dosim. 38(1/3)

Lung deposition peaks at 40-60% for 30 nm UPTracheal deposition is 20-40% for <10 nm UP

Potential Particulate Matter (PM) Health Indicators

• Ultrafine, fine, or coarse mass size fractions

• Mass, surface area, or number of particles

• Mass, sulfate, acidity, solubility, or transition metals

• Pollens, fungi, molds, or endotoxins

• Synergies with weather or other pollutants

1997 A&WMA Critical Review and Discussion Summary

What is now no longer true from 1997 Critical Review?

• “… weak biological plausibility has been the single largest stumbling block to accepting the association as causal.”

• “… evidence supporting development of chronic illness from long-term particle exposure … is weak.”

Vedal, 1997, JAWMA, 47(5)

Follow-up on PM and Health Effects

• Bates DV (2000). “Lines that connect: assessing the causality inference in the case of particulate pollution.” Environ Health Perspect 108:91-2.

• Pope CA III and Dockery DW (2006). “Health effects of fine particulate air pollution: lines that connect.”

2006 Critical Review and Discussion Summary

Pope and Dockery, 2006, JAWMA, 56(6); Chow et al., 2006, JAWMA, 56(10)

Key Aspects of 2006 Critical Review

• Short-term exposure and mortality

• Long-term exposure and mortality

• Time-scales of exposure

• Shape of concentration-response function

• Cardiovascular disease

• Biological plausibilityPope and Dockery, 2006, JAWMA, 56(6)

Recent Advances in PM Health Effects

• Short term exposure and mortality

– >100 time series studies; single & multiple cities

• Long term exposure and mortality

– Built around 6-City & ACS; growing prospective data base

• Time scales of exposure

– Varied time scales; distributed lags

Chow et al., 2006, JAWMA, 56(10)

Recent Advances in PM Health Effects (continued)

• Shape of the concentration response function

– Lack of apparent threshold; near-linearity through ‘0’

• Cardiovascular disease

– Cardiac events; changes in function; progressive disease

• Biologic plausibility

– Several prevailing theories – evidence for coherence with toxicology

Chow et al., 2006, JAWMA, 56(10)

PM10 O3

SO2 CO NO2

Stieb et al., 2002, JAWMA, 52(4)

Air Pollution Health Effects (Percent Excess Mortality)

Mortality risk in Harvard Six-City Study (Cohort Follow-up)

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

0 5 10 15 20 25 30 35

PM2.5 (mg/m3)

Mor

talit

y Ri

sk R

atio Steubenville

Topeka

Watertown

Kingston

St. Louis

Portage

Laden et al., 2006. Environ. Sci. Technol., 40(13)

*Associated with increments of 10 µg/m3 PM2.5 or 20 µg/m3 PM10 or British Smoke exposure Pope and Dockery, 2006, JAWMA, 56(6)

Days of Exposure

Mor

talit

y (%

)

Changes in Mortality Risk* in Exposure

Pope and Dockery, 2006, JAWMA, 56(6)

Cardiovascular Mortality Risks* in long-term exposure

Associated with increments of 10 µg/m3 PM2.5

Both fine and coarse PM induce health effects

EPA ORD, 2004, PM Criteria Document

Particle composition changes with size (Fresno, CA, USA)

UP Decreases Rapidly with Distance from Roadways

Reponen et al., 2003, J. Environ. Monit.

Health Effects of Ultrafine Particles (UP)

The lag (in days) between concentration and effect

CV: cardiovascular diseaseRE: respiratory disease

(Ibald-Mulli et al., 2002, J. Aerosol Med., 15(2))

Hypotheses on Toxicological Effects of UP

• Inflammatory (i.e., large surface area, react with macrophages and epithelial cells)

• Not efficiently removed by macrophages

• Contain or release more toxic free radicals

• Inhibit phagocytosis (i.e., unable to remove foreign substances)

• Translocate from lung to other organs via bloodstream or lymphatic system

• Effects enhanced by oxidant gases (e.g., ozone)

• Effects are most severe on the elderly and people with compromised respiratory tracts (e.g., chronic obstructive pulmonary disease)

(Sorensen et al., 2003, Mutation Research 544 (2-3))

Conceptual Model of UP/PM and Health Effects (different pathways)

Hypothesis on Interactions between UP and Respiratory System

(Donaldson et al., 2001, Occup. Environ. Med., 58(3))

Summary• Much progress has been made regarding PM

health effects

• Evidence of increasing cardiovascular effects in addition to pulmonary effects

• Better understanding of pathophysiological pathways to link PM-related mortality and morbidity

• Increasing research in the health effects of ultrafine particles

Knowledge Gaps

• Compliance air quality networks need to be designed for epidemiology studies. (Measurements at central site may not represent general population exposure.)

• Particle types and concentrations in toxicological studies are much higher and not representative of ambient air.

• Toxicological studies need to establish associations from animal subjects to humans.

Challenges Ahead

• Enhance air quality monitoring for research

• Assess toxicity of PM components

• Investigate health effects of long-term exposure to air pollutants

• Formulate multi-pollutant research programs

Simmons et al., 2004, NRC

Challenges Ahead (continued)

• Integrate across disciplines

– Design collaborative research

– Prioritize funding to multidisciplinary teams

– Encourage fellowships/sabbaticals

– Conduct joint workshop/meeting and publish proceedings and peer-reviewed summaries

Simmons et al., 2004, NRC